A pilot-scale upflow anaerobic sludge blanket (UASB) reactor was employed to treat the wastewater of a purified-terephthalic-acid (PTA) manufacturing factory. The performance of UASB reactor in terms of COD removal was achieved 62% at the volumetric loading rate of 2.93 kg COD / m3/day. One of the major constituents, p-toluic acid in PTA wastewater was the refractory component due to the methyl substituent on the aromatic ring, which restricted the biodegradation performance. Moreover, from our study, it was surprising that high concentration of acetic acid would retard the degradation of aromatics in the sludge bed. A control strategy of acetic acid level in the sludge bed was suggested during the start-up period. Comparison of the anaerobic biodegradability of aromatic substituents in PTA wastewater was concluded as the following sequence: –COOH > –CHO ≥ –CH3 in terms of the derivative functional groups based on the benzoic acid. Observation of bacterial population of the sludge granules showed high diversity of syntrophic structure on the biogranular surface as well as acetoclastic methanogens.

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